Method for treating nitrogen-containing polymeric dispersants

ABSTRACT

Method for treating nitrogen-containing polymeric dispersants for mineral lubricating oil compositions comprising heating the dispersant at a temperature in the range from about 200* to 400*C to effect a decomposition of the unstable components present in the dispersant, extracting said reacted or decomposed unstable components with a lower aliphatic alcohol and recovering a dispersant of improved thermal stability.

United States Patent 1 Chafetz et al.

[ Jan. 29, 1974 METHOD FOR TREATING NITROGEN-CONTAINING POLYMERICDISPERSANTS Inventors: Harry Chatetz, Poughkeepsie;

William P. Cullen, Fishkill; Edward F. Miller, Beacon, all of NY.

Assignee: Texaco Inc., New York, NY.

Filed: Nov. 12, 1971 Appl. No.: 198,468

US. Cl. 260/583 N, 260/583 P, 260/132, 260/133, 260/135, 252/47 Int. ClC07g 17/00 Field of Search.... 260/583 N, 583 P, 132, 133, 260/135References Cited UNITED STATES PATENTS 8/1969 Anderson et al. 252/47Primary ExaminerLewis Gotts Assistant Examiner-D. R. Phillips Attorney,Agent, or Firm-Thomas H. Whaley et a1.

[5 7] ABSTRACT 11 Claims, N0 Drawings METHOD FOR TREATINGNITROGEN-CONTAINING POLYMERIC DISPERSANTS BACKGROUND OF THE INVENTION 1.Field of the Invention This invention is concerned withnitrogen-containing polymeric dispersant employed in lubricating oilcompositions. Modern lubricating oil compositions for internalcombustion engines contain a dispersant which functions to keep anyimpurities suspended in the lubricating oil so that they can be removedby the oil filter in the lubrication system.

In general, the dispersant is a nitrogen-containing polymeric materialwhich has the ability to disperse and maintain in suspension any foreigninsoluble material present in the lubricating oil.

The nitrogen-containing polymeric dispersants currently in use arehighly effective against sludge and varnish formation under stop and gotype driving conditions. The high temperature performance of thesenitrogen-containing polymeric dispersants, however, is not satisfactory.In particular, many of the nitrogencontaining polymeric dispersants donot provide adequate protection against the formation of varnish at hightemperatures, a deficiency which showed up when they were employed in alubricating oil composition in diesel engine service. It has beenpostulated that this defect is due to the presence of thermally unstablecompounds in the nitrogen-containing polymeric dispersant which at ahigh temperature cause or contribute to the formation of varnish in theengine.

2. DESCRIPTION OF THE PRIOR ART No art is known which describes a methodfor treating nitrogen-containing polymeric dispersants for motor oils soas to improve their sludge and varnish resistant properties under hightemperature engines operating conditions.

SUMMARY OF THE INVENTION The method of the invention comprises treatinga nitrogen-containing polymeric dispersant for a lubricating oilcomposition having unstable components by heating the dispersant at aneffective temperature and for sufficient time to decompose said unstablecomponents present in the dispersant and thereafter extracting thedecomposed unstable components with a lower aliphatic alcohol.

More particularly, this method involves heating an oil-solublenitrogen-containing polymeric lubricating oil dispersant, characterizedby containing from about 0.5 to 6 percent nitrogen and by an averagemolecular weight ranging from about 500 to 50,000 at a temperaturegenerally in the range of 200 to 400C until substantially all of thethermally unstable components have been decomposed and solventextracting the decomposed unstable components from thenitrogencontaining polymeric dispersant with an aliphatic alcohol havingfrom 1 to 6 carbon atoms.

The method of this invention is relatively simple to conduct. Inpractice, the prescribed liquid nitrogencontaining polymeric dispersantis heated in a suitable vessel to a temperature generally ranging fromabout 200 to 400C, preferably from 250 to 300C, desirably with agitationor stirring of the mixture in order to insure even heat distribution andavoidance of hot spots. The elevated reaction temperature is maintaineduntil a substantial portion or all of the unstable components in thedispersant have been decomposed. This will generally be evidenced by aloss of nitrogen from the dispersant and the nitrogen content of thedispersant can be monitored during the process as an indication of thecompleteness of the treatment. The decomposed unstable componenets mustbe removed or separated from the heat-treated reaction product. They areseparated from the heattreated dispersant by solvent extraction with analiphatic alcohol. Specifically, aliphatic alcohols having from 1 to 6carbon atoms such as methanol, ethanol, isopropanol, butanol andmixtures thereof are employed to extract the decomposed unstablecomponents. The mechanism of the reaction is not fully understood, butit is postulated that the unstable components in the dispersant aredecomposed during the heat treatment and are substantially removed fromthe dispersant in the above-noted extraction.

The duration of time for effecting the decomposition reaction is notcritical. It will be understood that this time will be affected by thetemperature and the amount of agitation employed and that the progressof the decomposition reaction can be monitored as noted above.

A variety of nitrogen-containing polymeric disper sants can bebenefitted by the reaction of this invention. In general, thenitrogen-containing polymeric dispersants are oil'soluble mixtures ofcompounds formed from the reaction of a high molecular weight polymericmaterial and a nitrogen-containing compound, such as an amine or apolyamine. The nitrogen-containing polymeric dispersant reaction productis characterized by containing from about 0.5 to about 6 weight percentof nitrogen in the polymer and having a molecular weight averaging fromabout 500 to about 50,000. The most effective and preferrednitrogen-containing polymeric dispersants for employment in the processof the invention contain from about 1 to 3 percent nitrogen and have anaverage molecular weight ranging from about 700 to about 3000.

N-polyamine-substituted-alkenyl succinimides represent a class ofnitrogen-containing polymeric dispersants which can be bencfitted by theprocess of the invention. These materials can be prepared by reacting analkenyl succinic acid anhydride having the formula:

' in which R is a hydrocarbon radical having a molecuin which x is aninteger from 1 to 6 and R is hydrogen or a low molecular weight alkylradical.

R in the first formula above represents a hydrocarbon radical preferablyderived from the olefin containing from 2 to 5 carbon atoms. Suitableolefins from which R is derived are ethylene, propylene, l-buteneisobutylene, l-amylene, 2-amylene and the like. The R radical generallyhas a molecular weight ranging from about 400 to 3000 corresponding toapproximately 30 to 200 carbon atoms, with a preferred molecular weightbeing from about 800 to 1,500.

R in the polymaine represents hydrogen or a low molecular weight alkylradical having from 1 to 3 carbon atoms, x is an integer from 1 to about6 and preferably from 2 to 5. Suitable polyamincs or polyalkylenepolyamines for preparing the reaction product are ethylene diamine,propylene diamine, butylene diamine, diethylene triamine, triethylenetetramine, tetraethylene pentamine, pentaethylene hexamine, dipropylenetriamine, tripropylene tetramine, dimethylaminoethylamine,dimethylaminopropylamine and diethylaminopropylamine.

From one-half to two moles of the polyamine are reacted with one mole ofthe alkenyl succinic acid anhydride to form the reaction product. It ispreferred to react approximately one mole of the alkenyl succinic acidanhydride with one mole of the polyamine. The reaction is normallyeffected at a temperature up to about 200C. The preparation of this typereaction product is described in U.S. Pat. No. 3,131,150 and U.S. Pat.No. 3,172,892 and the disclosures of these patents are incorporated inthe present application.

Another type of nitrogen-containing polymeric dispersant which can beimproved by the present process are the oil-soluble polyalkylenepolyamine derived dispersants. These nitrogenous dispersants canconveniently be prepared by reacting a halogenated polyolefin with apolyalkylene polyamine. In general, a halogen-containing polymercontaining from 25 to 500 carbon atoms, such as the chlorinated polymerof propylene, ethylene-propylene, ethylene, butylene, is butylene andthe like, is reacted with a polyalkylene polyamine such asethylenediamine, 1,3-propanediamine, 1,6-hexanediamine,tetraethylenepentamine, pentaethylenehexamine, iminobispropylamine,N-aminoethylpiperazine and polyalkylene polyamines in general having amolecular weight from about 60 to 300. The resulting products areoil-soluble nitrogencontaining dispersants containing from about 0.5 to6 percent nitrogen and having a molecular weight ranging from 1,200 tosubstantially above 50,000. The materials are more fully described inU.S. Pat. No. 3,275,554 and 3,565,804 wherein their use as lube oiladditives is described. The disclosures of these references areincorporated in the present application.

The high temperature performance of nitrogencontaining polymericdispersants derived from sulfurized polymers can be greatly improved bythis method.

These materials are prepared by reacting polymers having a molecularweight range of about 400 to 50,000 derived preferably from C -Colefins, with sulfur at an elevated temperature in the range of 150 to300C and subsequent reaction with amines. These amines includepolyalkylenepolyamines of the general formula:

where R is a hydrogen or a low molecular weight alkyl radical havingfrom 1 to 4 carbon atoms and x is an integer from l to 6. Other suitableamines are 1,3-'

propanediamine, 1,4-butanediamine, 1,6-

hexanediamine and the like as described in the sulphurfree materialsreferred to above. The sulphurcontaining polymers will generally containfrom about 0.5 to 5 percent sulphur. Polymers of the type described inU.S. Pat. No. 3,459,664 containing trithione polyamine reaction productsare improved by the instant process. 1

EXAMPLE I 4,200 grams (3.0 moles) sulphurized polyisobutylene having themolecular weight of about 1,200 and containing 7.6 percent sulphur and2,646 grams (14.0 moles) tetraethylene pentamine were heated at 200C for6 hours. The reaction mixture was diluted with heptane, extracted with amethyl alcohol-iso-propyl alcohol mixture and stripped under vaccuum toC. The reaction product amounted to 3,800 grams and has the followinganalysis:

% Nitrogen 1.4 Sulphur 3.8 Total Base Number 30.9

A portion of the above reaction product was heated to a temperature of250C for 20 hours with mechanical stirring and a nitrogen purge. Thisreaction mixture was then cooled, diluted with 30 percent mineral oil,diluted with heptane, extracted with a methyl alcoholisopropyl alcoholmixture and stripped of alcohol under vacuum. Analysis of theheat-treated reaction product corrected for the oil present was asfollows:

% Nitrogen 1.1 Sulphur 3.8 Total Base Number 27.2

The effectiveness of the method of the invention was determined byemploying both the heat-treated and untreated nitrogen-containingpolymeric dispersants described above in a conventional crankcaselubricating oil composition at a concentration to provide a nitrogencontent of about 0.07 percent and running these crankcase oils in adiesel engine test. Specifically, the lubricating oil compositions wereemployed in the Caterpillar l-H diesel engine test. The crankcaselubricant in this test encounters relatively high engine temperatureswhich causes the formation of substantial amounts of varnish deposits onthe piston of the engine. To pass the Caterpillar 1H engine test, thelubricant must be effective against the formation of varnish on thepiston skirts during the engine test.

Oil A is a conventional crankcase lubricant containing the untreateddispersant of Example I. Oil B is the same conventional crankcaselubricant containing the heat-treated and solvent-extracted dispersantof Examples l. The results obtained in the Caterpillar ll-l engine testtun are set forth in Table 1 below. The data shows the percentage offill in the top groove (TGF) and the percentages of varnish covering inthe first groove l-G, first land l-L, second groove 2-G, second land2-L, third groove 3-6 and the skirt area below the third groove.

TABLE l OIL A OIL B Test Duration (Hrs) 120 I TGF-Carbon I I0 l-GVarnish coverage 68 100 l-L I 84 30 2'6 41 0 2-L 6O 0 3-G 0 0 Below 3-GVarnish Clean The above data show extensive varnish formation on thepistons resulting from the use of Oil A in the Caterpillar l-H EngineTest. Oil B, containing the dispersant treated according to the processof the invention, prevented the formation of any varnish below the firstland and demonstrates a surprising improvement due to the use of theheat-treated nitrogen-containing dispersant.

3. A method according to claim 1 in which said nitrogen-containingpolymeric dispersant is characterized by containing from about 0.5 to 6percent nitrogen and ing is conducted at a temperature from about 250 toI having an average molecular weight ranging from about 500 to 50,000.

4. A method according to claim 1 in which said nitrogen-containingpolymeric dispersant is characterized by containing from about 1 to 3percent nitrogen and having an average molecular weight ranging fromabout 700 to 3,000.

5. A method according to claim 1 in which said nitrogen-containingpolymeric dispersant has an average molecular weight from about 800 to1,500.

6. A method according to claim 3 in which said dispersant is anN-polyamine-substituted alkenylsuccini-v mide.

7. A method according to claim 3 in which said dispersant is apolyolefin polyamine.

8. A method according to claim 7 in which said dispersant contains fromabout 0.5 to 5 percent combined sulphur.

9. A method according to claim 1 in which the extraction solvent for thedecomposed unstable components is methyl alcohol.

10. A method according to claim 1 in which the extraction solvent forthe decomposed unstable components is ethyl alcohol.

11. A method according to claim 1 in which the extraction solvent forthe decomposed unstable components is a mixture of methanol andisopropanol.

2. A method according to claim 1 in which said heating is conducted at atemperature from about 250* to 300*C.
 3. A method according to claim 1in which said nitrogen-containing polymeric dispersant is characterizedby containing from about 0.5 to 6 percent nitrogen and having an averagemolecular weight ranging from about 500 to 50,000.
 4. A method accordingto claim 1 in which said nitrogen-containing polymeric dispersant ischaracterized by containing from about 1 to 3 percent nitrogen andhaving an average molecular weight ranging from about 700 to 3,000.
 5. Amethod according to claim 1 in which said nitrogen-containing polymericdispersant has an average molecular weight from about 800 to 1,500.
 6. Amethod according to claim 3 in which said dispersant is anN-polyamine-substituted alkenylsuccinimide.
 7. A method according toclaim 3 in which said dispersant is a polyolefin polyamine.
 8. A methodaccording to claim 7 in which said dispersant contains from about 0.5 to5 percent combined sulphur.
 9. A method accordinG to claim 1 in whichthe extraction solvent for the decomposed unstable components is methylalcohol.
 10. A method according to claim 1 in which the extractionsolvent for the decomposed unstable components is ethyl alcohol.
 11. Amethod according to claim 1 in which the extraction solvent for thedecomposed unstable components is a mixture of methanol and isopropanol.